Impact of pore morphology on two-phase flow dynamics under wettability alteration

Abstract

Low salinity waterflooding aims to alter rock wettability from oil-wet towards less oil-wet or water-wet conditions. There is a limited understanding of how wettability alteration impacts two-phase flow, which is why it is unclear how wettability change impacts oil recovery. This study is an attempt to evaluate the effect of wettability alteration on two-phase flow for different pore size distributions under tertiary mode of low salinity waterflooding. Pore-scale, two-phase flow simulations with wettability alteration were performed in OpenFOAM’s CFD tool. Two synthetic pore geometries (domains) were constructed with identical pore topology and connectivity, but different variances of pore throat radii. In our simulations, the pore network with a larger variance in pore radii resulted in 12% additional oil recovery. Whereas, the network with smaller variance in pore radii experienced no additional oil recovery despite the same wettability alteration change. This implies that change of wettability in clusters with a larger variation of pore radii can lead to a larger variation in capillary pressure gradient due to wettability alteration, which induces remobilisation of the trapped oil.